Measuring Frequency Off-the-Air:
The ARRL Frequency Measuring Test

There are some unique challenges in measuring the frequency of signals
being received from distant stations. Interference, signal strength, and
the vagaries of the ionosphere all conspire to make it quite a challenge
to determine the frequency of an HF signal (in the range of 3 to 30MHz)
more accurately than a few parts in 107.

For decades up until 1981, the
American Radio Relay League ("ARRL"), the US national amateur radio
organization, ran tests by transmitting a carrier from its headquarters
station, W1AW, and inviting hams to measure its frequency; certificates
were given for those who came close to the official frequency. This activity
ended when the frequency synthesizers and digital displays used in ham
equipment became accurate enough that inadvertent out-of-band operation
was no longer a significant problem.

In 2002, however, the ARRL re-introduced the Frequency Measuring Test
("FMT") as an annual affair. Information about the FMT is available at
www.arrl.org/w1aw/fmt.
I've been an enthusiastic participant in all the recent tests (what a
surprise!).